Review of Water Flow in Soils, 2nd Ed., by Tsuyoshi MiyazakiWater Flow in SoilsTaylor & Francis Group

Abstract

This book is composed of nine chapters. The first six chapters and the last chapter are written by Miyazaki; Chapter 7 is co-authored with K. Seki, and Chapter 8 with S. Hasegawa and T. Kasubuchi. For an authored book this seems an unusual arrangement. Introducing the system of units employed in the book, Chapter 1 discusses the structure of soils and the retentivity of water therein. The structure includes both solid phase and soil pores, as well as liquid phase and gas phase in soil pores. Matric potential, soil moisture characteristic curves, osmotic effect on retentitivity, and hysteresis encompass the material on the retentivity of water in soils. Chapter 2, containing five parts, discusses physical laws of water flow in soils. Introducing Darcy’s law for water flux in one, two, and three dimensions, the first part goes on to present basic equations governing the flow of water in soils, unsaturated hydraulic conductivity and empirical relations thereof, and soil water diffusivity without any mathematical relations. The second part discusses the gas-phase configuration in unsaturated flow, including free and entrapped air in soils, forced-closed system, water flow in open systems, and significance of gas-phase configuration in fields. The discussion is comprehensive and has a lot of significance in irrigated agriculture and hydrologic modeling, as well as solute transport. The third part is on infiltration and discusses basic aspects of infiltration and infiltration into dry soils and wet soils. Mathematical equations of infiltration included are Horton, Holtan, Green–Ampt, and Philip. There are other useful empirical and conceptual equations, such as Kostyakov, SCS-CN, Singh-Yu, Smith, Parlange, and others, that have been found to be useful in irrigation engineering and watershed modeling, but have not been included. Steady flows, both upward and downward, are discussed in Part IV. The last part deals with transient flow in soils, including evaporation, redistribution, and water flow in deep soils. The chapter is quite good but would have been stronger if it had a discussion on stochasticity and reliability of different formulations. A discussion of errors and limitations of different formulations is helpful to the reader. Refraction of water flow in soils is the subject matter of Chapter 3. It encompasses refraction of flux, theory of refraction, jump condition, visualization of refraction in layered soils, and verification of refraction theory experimentally as well as numerically. Refraction and anisotropy coefficient in saturated layered and unsaturated layered soils, and refractive anisotropy coefficient in two-layered and multilayered models, are also treated in the chapter. This provides a comprehensive treatment of refraction theory. Chapter 4 deals with preferential flow. Beginning with a classification of flow, it goes on to discuss general features; vertical and lateral bypassing flow; criteria and hydrodynamics of fingering flow; and nature, experimental observation, qualitative features, and modeling of funneled flow. Both saturated and